debug of multithreaded program turns to be impossible during execution

[Pedro Alves]

On 07/31/2014 10:27 AM, Avi Gozlan wrote:
> Hello,
> 
> I'm debugging a multithreaded program using GDB. Various threads are created and exit during execution. GDB copes successfully with the multiple threads (e.g. 'thread apply 3 bt' reports successfully backtrace of thread 3), but then at one point loses control of the program:
> 
> (gdb) c
> Continuing.
> [New Thread 0x41401940 (LWP 13370)]
>  [Thread 0x40a00940 (LWP 13333) exited]
> [New Thread 0x41e02940 (LWP 13371)]
> ...
> [New Thread 0x45a08940 (LWP 13377)]
> [New Thread 0x46409940 (LWP 13378)]
>  [Thread 0x41e02940 (LWP 13371) exited]
>  [Switching to Thread 0x45a08940 (LWP 13377)]
> Cannot remove breakpoints because program is no longer writable.
> Further execution is probably impossible.
> 0x00002aaaab98348f in start_thread () from /lib64/libpthread.so.0
> ptrace: No such process.
> 
> Surprisingly, although debugging is no more possible, the program is not dead:

I have a vague recollection that this was fixed a while ago.  Like,
GDB was picking the wrong thread to access memory, and it ended up
picking a running or exited thread, and that fails (in either
case ptrace complains the same say).

> GDB version: 7.6

Is there a chance you could try a more recent GDB version?  Ideally
7.8, which we just released.

Thanks,
Pedro Alves